We meet Veronica Callahan, a very smart nurse who returns to Mercy Hospital after a year long tour of service in the Army. She's not afraid to take risks in order to save her patients, but this attitude might just cost her her job. In her personal life she's trying to make her marriage work with her high school sweetheart Mike, but when she sees the hospital new doctor it might not be that simple. Meanwhile, we meet Veronica's best friend and also nurse colleague Sonia, who thinks she finally found the man of her life and also Chloe, a rookie nurse who is learning the hard way how to be a nurse.

Veronica and her husband Mike try to rekindle their romance and move back in together, but this might not be as simple as they thought. At the hospital, Veronica and Dr.Sands try to just be friends but it's also not that easy. Meanwhile, Sonia is in love with the hunky cop Nick Valentino, who turns out to be more compatible with her than she thought. He helps her also with a Jane Doe case, while Chloe tries to help a patient everyone has already given up on.

As her affair with Dr. Sands surfaces, Veronica contemplates to come clean to her husband. Sonia gets relationship advice from a patient and questions her approach to dating, just as her boyfriend goes missing. Meanwhile, Chloe reunites with an ex-boyfriend but her plans take an unexpected turn when she learns some news.

After Veronica's affair becomes public, she and Mike reunite in a family crisis from Veronica's side. Meanwhile, Sonia is agitated when her high school rival comes to the hospital and ends up being her patient. Only to discover that the life of her rival life is not as perfect as she though. Later, things heat up between Chloe and her fireman, while Dr. Sands moves on from Veronica to another Mercy staffer.

Veronica (Taylor Schilling) helps a patient cope after a terrifying experience on the operating table launches him into a crisis of faith. Meanwhile, she suspects that Mike (Diego Klattenhoff) has moved on and started dating again. Sonia (Jaime Lee Kirchner) tries to track down the next of kin for a young patient after a car accident, but instead uncovers a terrible secret that will change the girl’s life forever. And Chloe (Michelle Trachtenberg) mediates a bitter family feud when her patient’s children can’t agree on a course of treatment for their dying father. James Tupper, James Le Gros, and Guillermo Diaz also star.

Veronica takes an extra shift at the Hospital in order to spend more time with Dr. Sands and to avoid her recurrent PTSD symptoms triggered by the robbery. But when she makes a terrible discovery about a young patient, her reaction to it shock everyone even herself. Meanwhile, Sonia confronts an ethical decision when her home-care patient tries to end her life, while Chloe gets the surprise of her life while she accompanies Dr. Briggs to a VIP house call.

Veronica treats a patient for an anorexic disorder who is almost as good as Veronica herself in the denial department. When Dr. Sands and Veronica's family confront her after St. Patrick's Day binge, she considers seeing a therapist. Meanwhile, after working with Dr. Briggs to save a heart attack patient, Chloe softens to Dr. Briggs after she learn his true reasons for becoming a doctor. While Sonia, still is silently mourning her home-care patient, she unexpectedly runs into her ex-boyfriend at St. Patrick's Day fair.

When two boys get trapped in an abandoned building, Veronica finds herself in the right place at the right time to help them. Back at the hospital, Chloe pressures doctors to perform a risky surgery to save her comatose boyfriend from brain death, and Sonia treats a psychic patient who makes a mysterious prediction about her future. Meanwhile, Briggs tries frantically to raise the funds needed to pay off his high-stakes debt with the mafia before it's too late, and Sands considers a job offer to return to Afghanistan.